1. Field of the Invention
This invention relates to a granular detergent having a specially selected combination of water-soluble anionic surfactants and water-insoluble nonionic surfactants. The detergent exhibits improved cleaning ability with respect to oily and greasy soil.
2. Description of Related Art
U.S. Pat. No. 3,849,347 describes a gel-like detergent for pretreating grease-soiled fabrics. The detergent contains a mixture of a lipophilic nonionic surfactant and an anionic alkylbenzene sulfonate surfactant. Examples of the nonionic surfactant component include the adduct of a 70:30 (by weight) mixture of lauryl alcohol and myristyl alcohol and 3 moles of ethylene oxide per mole of alcohol and the adduct of nonylphenol and 5 moles of ethylene oxide. The preferred anionic surfactant is a linear alkylbenzenesulfonate in which the alkyl group has 10-15 carbon atoms.
Use of this detergent, however, is difficult and time consuming because it involves pretreatment of fabrics with the gel for about 30 minutes before loading into the washing machine. Unfortunately, these detergents generally are difficult to incorporate in a standard, granular multipurpose detergent because of their gel-like character.
U.S. Pat. No. 3,925,224 discloses that the addition of a water-insoluble surfactant composition to detergents containing standard water-soluble, anionic, nonionic or zwitter-ionic surfactants produces an increase in detergency. Primary alcohol-ethylene oxide adducts containing from 12 to 15 carbon atoms in the alcohol chain and an average 3 ethylene oxide groups (EO), octylphenol-ethylene oxide adducts containing 3 (EO) groups and cocosamine-ethylene oxide adducts containing 2 (EO) groups are specifically mentioned as examples of the water-insoluble surfactant.
The water-insoluble surfactant additive is added separately to the detergent or wash liquor in the form of a liquid or solid. Solid additives may contain from 0.1 to 60% by weight of the water-soluble surfactant composition, which also embraces mixtures of water-insoluble and water-soluble surfactants, and from 99.9 to 40% by weight of builder salts, fillers, bleaches and other detergent ingredients. Preferably, the additive contains 0.5 to 20%, more particularly, 1 to 10% and most particularly from 1 to 5% by weight of the water-insoluble surfactant. The water-insoluble surfactants may be dry-mixed into the detergent additive composition rather than by spray-drying so that surfactant losses through "pluming" in the spray drying tower is not a problem.
Nonionic surfactants having a low degree of ethoxylation are oily. These surfactants are difficult to incorporate in standard granular detergents in relatively large quantities, i.e., in quantities exceeding 5% to 8%, because they impair the detergent's free-flowing properties. U.S. Pat. No. 3,925,224 does not suggest how relatively large quantities of these surfactants, i.e., quantities of up to 60% by weight, can be incorporated in powdered detergents without adversely affecting their fluidity. Generally, spray-drying is out of the question because of the pronounced tendency of these components towards "pluming" in the off-gases of the spray-drying tower.
Accordingly, it is an important object of the present invention to provide a granular detergent which is distinguished by its high detergency, particularly with respect to oily and greasy soil. A further object of the invention is a granular detergent formulation having detergency-boosting additives which do not adversely effect the free-flowing properties of the detergent and which do not contribute to undesirable pluming in the spray-drying tower during production of the detergent.